1. Field of the Invention
The present invention relates to a solution for broadening the applicability of digital printing techniques. More specifically, the present invention is related to a digital press adapted for being compatible with other non-digital printing press types.
2. Description of the Related Art
Digital printing is known from the office and home market, where xerography (toner) or ink jet technology are used for document printing. In the wide format printing market, ink jetting is being used for printing signs, advertising at POS (Point of Sale), car fleet decoration, etc.
Outside the office and home market, various printer configurations have been developed for digital printing on various information-carrying materials such as paper, adhesive vinyl, fabrics, and PVC. Two such configurations are the so-called “roll-to-roll” and “flatbed” configurations. In general terms, “roll-to-roll” printers utilize a transport system configured to displace a flexible sheet in a given feed direction with respect to a print head by means of rollers. As for “flatbed” (also called “rigid”) printers, their transport system utilizes a rigid support for a sheet (not necessarily flexible) or a rigid sheet driven for back and forward movement with respect to a print head. In all printing technologies, transport systems need to provide a high level of accuracy in registering a sheet (generally, information-carrying material) and ensuring accurate positioning of the print head over the information-carrying material, for precise printing.
The more industrial type digital printers include a “flatbed” type transport system that allows them to print on both flexible and rigid sheets. Some of the printing equipment suppliers active in this market are Inca Digital Printers (e.g., the Columbia Turbo printer), Durst (e.g., the Rho 205 printer), Vutek (e.g., the PressVu UV 180 printer), and Zund (e.g., the UVjet 215c printer). These suppliers provide printers having a flatbed transport system for feeding a printing sheet in a feeding direction and a shuttle system for traversing a print head across the printing sheet in a direction perpendicular to the feeding direction of the printing sheet. The flatbed transport system and the shuttle system cooperate together to make the desired print on the printing sheet as a collection of adjacent print swaths. A print swath is printed when the shuttle system moves the print head across the printing sheet while the flat-bed transport system holds the printing sheet in a fixed position. The flatbed transport system then advances the printing sheet with an increment corresponding to the width of the print swath and a next print swath is printed during a next movement of the shuttle system while the printing sheet is again maintained in a fixed position. The movement of the print head or shuttle system relative to the printing sheet may also be implemented the other way around, i.e., printing of a print swath occurs when the printing sheet moves back and forth while the print head or shuttle system moves with incremental steps between the printing of the swaths. Printers using this approach are known from Inca Digital Printers, e.g., the Columbia flat bed printer. Recent patent literature disclosing flatbed arrangements for digital printers, possibly combined with a roll-to-roll system, includes WO-A 2004/037543 to NUR Macroprinters, WO-A 2004/002746 to Inca Digital Printers, and U.S. Pat. No. 6,296,403 to Scitex Vision. In the patent documents, the direction of movement during which a print swath is printed is often referred to as the fast scan direction, whereas the other direction of movement during which the print head and/or the printing sheet are repositioned relative to each other for enabling printing of a next print swath is referred to as the slow scan direction.
One of the advantages of digital printing as opposed to conventional printing, like offset or screen printing, is that process colors can be printed very easily, i.e., the color information that can be reproduced with a mixture of primary and/or secondary colors such as a combination of Cyan, Magenta, Yellow and blacK. It often requires only one 4-color digital print station to reproduce these colors, whereas it requires four single-color offset or screen print stations to do the same. Digital printing, however, fails to provide acceptable solutions for applications where “industrial inks” as spot colors (e.g., brand color), metallic colors (e.g., gold), conductive material (e.g., copper), varnishes, white pre-coats, etc. are to be printed on an information-carrying material. These industrial inks are often not printable with digital printing technologies or require very specialized and dedicated chemistry or equipment to condition these inks for printing with digital technology. A lot of these industrial inks are nowadays printed with screen printing technology.
It would therefore be advantageous to have a digital printing system that can easily be extended with a conventional printing system to support printing of “industrial inks” inline with the printing of the process colors in the digital printing system.